Non-woven fiber processing methods may include such examples as electrospinning and melt blowing. Electrospinning involves applying a sufficiently high voltage to a liquid droplet expelled under pressure from a spinning tip. As the spun liquid dries, the charged substance is elongated by electrostatic repulsion as it travels through the air and dries and eventually deposited on a grounded collector. Melt blowing involves extruding a polymer melt from a small nozzle surrounded by high speed gas. The blowing elongates the fibers and randomly deposits the fibers in a nonwoven sheet.
Electrospinning cannot always achieve the smaller fiber diameters, especially for high viscosity polymer melts. Therefore, lower molecular weight polymers are usually required to achieve lower fiber sizes. Lower novel sizes must also be used to achieve the lower diameter fiber sizes, which greatly impede the production of such fibers on any large scale. The electrospinning technique is inherently slow and solvent intensive. Moreover, the available polymers are limited. Melt blowing processes generally achieve microfiber sizes in the diameter range of 2-4 μm. Attempts at smaller fiber sizes have been attempted. However, production is similarly limited and not scalable to larger production quantities or not available across different molecular weight polymers.
Examples of systems for producing nonwoven fibers can be found in, for example, U.S. Pat. No. 3,849,241, issued Nov. 19, 1974; USPN 2005/0053782, published Mar. 10, 2005; and US 2017/0016146, published Jan. 19, 2017, each of which is incorporated in its entirety herein.